Inspection systems, circuits, and methods are provided to enhance defect
detection by reducing thermal damage to large particles by dynamically
altering the incident laser beam power level supplied to the specimen
during a surface inspection scan. In one embodiment, an inspection system
includes an illumination subsystem for directing light to a specimen at a
first power level, a detection subsystem for detecting light scattered
from the specimen, and a power attenuator subsystem for dynamically
altering the power level directed to the specimen based on the scattered
light detected from the specimen. For example, the power attenuator
subsystem may reduce the directed light to a second power level, which is
lower than the first, if the detected scattered light exceeds a
predetermined threshold level. In addition reducing thermal damage, the
systems and methods described herein may be used to extend the
measurement detection range of an inspection system by providing a
variable-power inspection system.